Spinel is an important class of oxides consisting of two types of metal ions with the oxide ions arranged inCCP pattern. The normal spinel has 1/ 8 of the tetrahedral holes occupied by one type of metal ion and 1/2 of the octahedral holes occupied by another type of metal ion. Such a spinel is formed by Zn2+, A13* and 02-with Zn2+ in the tetrahedral holes. If CCP arrangement of oxide ions remains undistorted in the presence of all the cations, formula of spinel and fraction of the packing fraction of crystal are respectively :

(1) ZnAl2O4 , 77%

(2) ZnAl2O4, 74%

(3) Zn2AlO4, 74%

(4) Zn3Al2O6,74%

Subtopic:  Introduction & Crystal System |
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What is the maximum number of layers of atoms in close-packed planes that will lie within two imaginary parallel planes having a distance between them of 1323 R (where R is the radius of an atom) in the copper crystal (FCC)?
Consider the atoms to be within the parallel planes if their centers are on or within the two parallel planes.

1. 5

2. 6

3. 7

4. 8

Subtopic:  Introduction & Crystal System |
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Analysis show that nickel oxide consist of nickel ion with 96% ions having d8 configuration and 4% having d7 configuration. Which amongst the following best represents the formula of the oxide.

(1) Ni1.02O1.00

(2) Ni0.96O1.00

(3) Ni0.96O0.98

(4) Ni0.98O1.00

Subtopic:  Density & Packing Fraction |
 54%
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PCl5 molecule has

(1) three fold axis of symmetry

(2) two fold axis of symmetry

(3) both

(4) none of these

Subtopic:  Introduction & Crystal System |
 55%
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Which of the following statements is correct about the conduction of electricity in pure crystal of silicon atroom temperature?

(1) The conduction is due to electrons present in fully occupied lowest energy states.

(2) The conduction is due to only some electrons capable of leaving the bonds at room temperature.

(3) The conduction is only due to the holes formed from the release of electrons.

(4) The conduction is due to the movement of both the electrons released and holes formed.

Subtopic:  Density & Packing Fraction |
 56%
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Calculate the Miller indices of crystal planes which cut through the crystal axes at (i) (2a, 3b, c), (ii) (∞, 2b, c )

(1) 3, 2, 6 and 0, 1, 2

(2) 4, 2, 6 and 0, 2, 1

(3) 6, 2, 3 and 0, 0, 1

(4) 7, 2, 3 and 1, 1, 1

Subtopic:  Introduction & Crystal System |
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Caculate the distance between 111 planes in a crystal of Ca. Repeat the calculation for the 222 planes. (a = 0.556nm)

(1) 016.1 nm

(2) 0.161 nm

(3) 0.610 nm

(4) None of the above

Subtopic:  Density & Packing Fraction |
 62%
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A metallic element crystallizes into a lattice containing a sequence of layers of ABABAB ............ Any packing of spheres leaves out voids in the lattice. The percentage by volume of empty space of this is

(1) 26%

(2) 21%

(3) 18%

(4) 16 %

Subtopic:  Introduction & Crystal System |
 86%
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Silver metal crystallises in a cubic closest – packed arrangement with the edge of the unit cell having a length a = 407 pm. What is the radius of silver atom.

(1) 143.9 pm

(2) 15.6 pm

(3) 11.59 pm

(4) 13.61 pm

Subtopic:  Introduction & Crystal System | Density & Packing Fraction |
 79%
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From the fact that the length of the side of a unit cell of lithium is 351 pm. Calculate its

atomic radius. Lithium forms body-centered cubic crystals.

(1) 152.69 pm

(2) 62.71 pm

(3) 151.98 pm

(4) 54.61 pm

Subtopic:  Introduction & Crystal System |
 76%
From NCERT
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